Programmable ion-protein networks from sodium caseinate: a sustainable platform for soft functional materials

Area of Science:

• Materials Science
• Biomaterials Engineering
• Soft Matter Physics

Background:

• Ion-protein coordination is an emerging strategy for designing advanced soft materials.
• Protein-based hydrogels offer sustainable and biocompatible alternatives to synthetic polymers.

Purpose of the Study:

• To investigate the influence of multivalent cations on the network architecture and properties of sodium caseinate hydrogels.
• To demonstrate the application of these ionically crosslinked hydrogels in developing high-performance soft sensors.

Main Methods:

• Systematic screening of various multivalent cations (Ca2+, Sr2+, Ba2+, Mn2+, Cu2+, Zn2+, Fe3+, Al3+, Zr4+) to crosslink sodium caseinate.
• Multimodal characterization including compositional, structural, morphological, thermal, spectroscopic, and mechanical analyses.
• Fabrication and testing of piezoresistive soft sensors using optimized caseinate-gelatin organohydrogel matrices.

Main Results:

• Ion selection demonstrated precise control over mechanical stiffness (1.5 kPa to 1.8 MPa), thermal stability, and hierarchical network architecture.
• Developed M^X+-caseinate (MCas) networks with an empirical packing hierarchy.
• Proof-of-concept soft sensors exhibited linear responses and competitive gauge factors (1.84-2.20), capable of detecting bending angles and dynamic inputs.

Conclusions:

• Sodium caseinate serves as a sustainable, ion-tunable platform for creating mechanically programmable protein hydrogels.
• This approach enables rational design of bioinspired materials for soft electronics and wearable sensing applications.
• Ion-specific crosslinking offers a powerful tool for tailoring hydrogel properties for advanced functional materials.